plants Article Contribution to the Orophilous Cushion-Like Vegetation of Central-Southern and Insular Greece Carmelo Maria Musarella 1,* , Salvatore Brullo 2 and Gianpietro Giusso del Galdo 2 1 Department of AGRARIA, Mediterranean University of Reggio Calabria, 89122 Reggio Calabria, Italy 2 Department of Biological, Geological and Environmental Sciences, University of Catania, 95125 Catania, Italy; [email protected] (S.B.); [email protected] (G.G.d.G.) * Correspondence: [email protected] Received: 22 July 2020; Accepted: 5 November 2020; Published: 30 November 2020 Abstract: The results of a phytosociological investigation regarding the orophilous cushion-like vegetation occurring in the top of the high mountains of central-southern Greece and in some Ionian (Lefkas, Cephalonia) and Aegean Islands (Euboea, Samos, Lesvos, Chios and Thassos) are provided. Based on 680 phytosociological relevès (460 unpublished and 220 from literature), a new syntaxonomical arrangement is proposed with the description of a new class, including two new orders, eight new alliances, and several associations (many of them new). Compared to the previous hierarchical framework usually followed in the literature, this study provides a more realistic and clear phytosociological characterization of this peculiar and archaic vegetation type, which is exclusive to the high mountains of the north-eastern Mediterranean. The new arrangement is mainly based on the phytogeographical role of the orophytes featuring this very specialized vegetation, which is essentially represented by endemics or rare species belonging to the ancient Mediterranean Tertiary flora. In addition, taxonomic research on the orophilous flora occurring in these plant communities allowed to identify six species new to science (i.e., Astragalus corinthiacus, Allium cremnophilum, A. cylleneum, A. orosamium, A. karvounis, and A. lefkadensis) and a new subspecies (i.e., Allium hirtovaginatum subsp. samium), and two new combinations (i.e., Astragalus rumelicus subsp. euboicus and subsp. taygeticus) are proposed. Keywords: phytosociology; flora; high mountain vegetation; Greece; taxonomy; Astragalus; Allium 1. Introduction The orophilous cushion-like vegetation colonizing the cacuminal stands of the highest mountains of the Mediterranean territories has always aroused a lot of interest from botanists, mainly for the occurrence of a peculiar and specialized flora. It is represented usually by relict taxa (species and subspecies), mainly endemic adapted to hard environmental conditions, which are aggregated in physiognomically well differentiated plant communities [1,2]. Many plants that characterize these phytocoenoses (usually localized at high altitude) belong to the ancient Tertiary Mediterranean flora. They are represented mostly by dwarf nanophanerophytes and chamaephytes mixed with caespitose hemicryptophytes which form plant communities often covering large surfaces. This ecologically specialized vegetation is associated and adapted to long wintry periods of lasting snow cover (sometimes till late spring), as well as to prolonged summer droughts with intense winds. It occurs mostly on rocky places with undeveloped and immature soils due to the prevailing harsh climatic conditions and wide diurnal and annual variations. Such factors seem to converge to climatic conditions of the temperate cold climate inserted in the Mediterranean context [3]. Plants 2020, 9, 1678; doi:10.3390/plants9121678 www.mdpi.com/journal/plants Plants 2020, 9, 1678 2 of 141 This leads to a strong contrast between the winter-spring period, which is very rigid and cold, and that summer-autumn one, generally very hot and dry. Therefore, the plants that thrive in these high-mountain stands (generally ranging from about 1000 to 4000 m of elevation in Mediterranean area are evolutionarily adapted to very peculiar climatic conditions shaping significant ecological specializations and concomitant range restrictions, that, in most cases, not allows them to live outside of these habitats. Therefore, they can be considered as typical Mediterranean orophytes that often have well circumscribed or punctiform distribution patterns and are well differentiated taxonomically from other closely related taxa. Among these high-mountain plants, it is possible to identify vicariants due to speciation processes and geographical or ecological isolation. The occurrence of dwarf shrubs in these Mediterranean mountains is very significant; such species have a typical thorny and compact cushion-like habit, inside which many delicate herbaceous species take refuge due to higher humidity compared to the exterior one, with their vegetative and floral structures protruding from them. Among these, an important physiognomic-structural role is played mainly by thorny species of Astragalus, which often dominate in many plant communities. In the central and western Mediterranean few of species belonging to this group of Astragalus usually occur. They are mainly represented by endemic species disjunctly distributed among some mountain tops, for example: Astragalus granatensis Lam. in Spain and northern Africa, A. nevadensis Boiss. in southern Spain, A. genargenteus Moris and A. gennarii Bacchetta & Brullo in Sardinia, A. greuteri Bacchetta & Brullo in Corsica, A. calabricus Fischer in Calabria, A. sirinicus Ten. in southern Apennines, while in Sicily there are A. siculus Biv. in the Etna volcano and A. nebrodensis Guss. in the Madonie massif [4]. Conversely, Astragalus species with tragacanthoid habit are much more numerous and widespread in the mountains of the eastern Mediterranean territories, which reach their maximum diversity in Anatolia. In particular, in the mountains of the Balkan Peninsula and of some Aegean islands the species of thorny Astragalus are more frequent, such as: A. angustifolius Lam. s.l., A. rumelicus Bunge s.l., A. creticus Lam., A. cylleneus Boiss. & Heldr., Astragalus calavrytensis Beauverd & Topali, A. cephalonicus C. Presl, A. thymphresteus Boiss. & Spruner, A. parnassi Boiss., A. taygeteus Persson & Strid, A. thracicus Griseb., A. condensatus Ledeb., Astragalus lesbiacus P. Candargy, A. dolinicolus Brullo & Giusso, etc. [5]. Apart from the Astragalus sp.pl., there are also other orophytes belonging to other genera or species complex that are characterised by morphological peculiarities and ecological adaptations, which are well distinct from other ones closely related taxa found in coastal or hilly places (geographical or ecological vicariants). In the eastern Mediterranean area, the following groups of taxa can be quoted as examples: (a) Cerastium candidissimum Correns, replaced in the Apennines and Sicily by C. tomentosum L., in Sardinia by C. supramontanum Arrigoni and in Corsica by C. soleirolii Duby [6–8]. (b) Marrubium cylleneum Boiss. & Heldr., distributed in the northern Peloponnese, which is vicaried by M. velutinum Sibth. & Sm. in the central Greece and M. thessalum Boiss. & Heldr. in the northern Balkans [9]. (c) Sideritis clandestina (Bory & Chaub.) Hayek is represented by the subsp. clandestina in the southern Peloponnese, and by the subsp. peloponnesiaca (Boiss. & Heldr.) Baden in northern Peloponnese, while it is vicariated by S. raeseri Boiss. & Heldr. subsp. raeseri in central and northern Greece, S. euboea Heldr. on the island of Evvoia, S. scardica Griseb. in the north and central Greece and former Yugoslavia, S. sipylea Boiss. in the eastern Aegean area, S. syriaca L. subsp. syriaca in Crete, S. sicula Ucrìa in Sicily and S. italica (Miller) Greuter & Burdet in the central-southern Italy [10,11]. (d) Nepeta argolica Bory ex Chaub. is distributed in the Peloponnese and Sterea Ellas, replaced by N. dirphya (Boiss.) Heldr. in Euboea, N. parnassica Heldr. & Sartr. ex Boiss. in the Mts. Parnassus and Chelmos, N. spruneri Boiss. in the North-central Greece, N. camphorata Boiss. & Heldr. in Taygetos, N. sphaciotica Davis in Crete, N. orphanidea Boiss. in Mt. Parnon and N. italica L. in Samos and West Anatolia [12]. (e) Carlina frigida Boiss. & Heldr. widespread in central-southern Greece, which is replaced by C. biebersteinii Hornem. subsp. brevibracteata (Andrae) K. Werner in the northern Balkans, Plants 2020, 9, 1678 3 of 141 C. curetum Heldr. in Crete, C. macrocephala Moris in Sardinia and Corsica, C. nebrodensis Guss. in Sicily and South Italy [13,14]. (f) Sesleria vaginalis Boiss. & Orph. widespread in Greece, replaced by S. robusta Schott et al. in the northern Balkans, S. anatolica Deyl in Samos and Anatolia, S. achtarovii Deyl in Thassos and eastern Balkans, S. nitida Ten. s.l. in Sicily and central-southern Apennines [13,15]. (g) Erysimum pusillum Bory & Chaub., endemic to southern Peloponnese, replaced by E. cephalonicum Polatsc. in northern Peloponnese and central Greece, E. parnassi (Boiss. & Heldr.) Hausskn. in the Parnassus, E. olympicum Boiss. in the Mount Olympus (Greece), E. mutabile Boiss. & Heldr. and E. raulinii Boiss. in Crete, E. bonannianum C.Presl and E. etnense Jord. in Sicily [13,16]. (h) Viola graeca (W. Becker) Halácsy, widespread in central Greece and northern Peloponnese, replaced in the southern Peloponnese by V. parnonia Kit Tan & al. in Mt. Parnon, V. sfikasiana Erben on Mt. Taygetos, V.euboea (Halácsy) Halácsy in Euboea, V.epirotica (Halácsy) Raus in Pindos ranges, Viola stojanowii W. Becker in Sterea Ellas, V. fragrans Sieber in Crete, V. nebrodensis C. Presl and V. aethnensis (Ging. & DC.) Strobl in Sicily, V. corsica Nyman in Corsica and Sardinia [13,17]. (i)